One of our first tasks was to design permanent frames for the large scintillators. A ladder-like construct was chosen to be a light and strong way to protect and support the 200 pound panels. 16 ft. boards were notched with a router for the crossbeams to fit, and joist hangers were used for extra support. The crossbeams themselves were notched to provide a snug cradle for the metal frame of the plastic scintillators. These crossbeams prevented sagging in the middle of the panel and lay under complementary supports in the metal frame. The wooden frame provides excellent support without adding significant weight. The panel frames have thick side boards for support and to enable sturdy stacking for coincidence testing. When designing the frame for the scintillator panels it was crucial to include sturdy support for the fragile PMTs on each end. Otherwise the PMTs are prone to being knocked off or damaged by accidental contact. PVC piping lined with foam padding was used to cradle the PMTs. The cradle was secured to the inside and bottom of the panel frame; thus providing ample support and protection. A sliding mechanism was also implemented to allow access to the PMT/panel connection without complete removal of the PMTs. Two different methods were used to attach the PMTs to the wave-shifting bar. The first consisted of a set of milled aluminum attachments designed for use with the Hamamatsu PMTs and these panels. A silicone cookie was placed between the PMT and the panel to provide mechanical protection and to minimize an air gap. For the second panel a foam shroud to hold an acrylic cookie was made and the PMT was attached using optical grease and electrical tape. Both resulted in excellent light transmission and efficient panels. The experimental setup consisted of a diffuse light source (a green LED embedded in an acrylic block with a small window to let out light) and a PMT placed in a darkbox. Using a picoammeter, output current from the PMTs was measured as a function of voltage. A gain curve was subsequently plotted for a range of 1.0 kV to 1.8 kV. Other components of the experiment included a pulse generator to regulate the 200 Hz LED flashes (a constant output from this LED would be enough light to burn out the PMTs), and an oscilloscope to view the output voltage pulses from the PMTs and the pulse width of the LED. The gain curves resulted in the choice of the Hamamatsu R5686 PMTs for use in the large scintillators due to their superior sensitivity and low dark current compared to the Thorn 9954B PMTs. In an effort to create the most efficient and symmetric detection with the panels we tested each panel with a series of Cs-137 gamma source runs. The source was placed over grid locations on the panel and the summed net current of both PMTs was averaged over 100 samples and recorded on a Keithley picoammeter with ExcelLinx. Because individual PMTs proved to have slightly different gain, we altered the voltages to get better symmetry. We also mapped individual PMT currents across the whole panel and determined that muon hits further than the middle of the board were not very likely to be detected by the opposite PMT. The serial connection between the DAQ and the computer is bits per second. The DAQ sends a 73 byte * 8 bit signal, which means at 100% efficiency the maximum speed of detection is about 32 hertz. By viewing the onboard hex counter the panel achieves about 180Hz, but only 30Hz was seen on the computer. This problem has been resolved by stripping down the signal by altering the assembly code on the DAQ. To test for light leaks the picoammeter was connected to the ExcelLinx program, which automatically records data to a spreadsheet. We averaged over 500 readings and calculated the standard error for each. The first test for each panel was a series of lights on/lights off tests to see if there was any significant difference in current. One of the panels showed a noticeable change in current with the lights on. We proceeded to use reading lamps to illuminate the top, then the bottom of the board, using a picoammeter to try to detect where the leak was located. We also used a black cloth to selectively shroud sections of the panel. The leak was found near a PMT on panel 6 (which was subsequently fixed). The other panel showed a 2 nA drop in current with the lights off. The leak couldn’t be isolated and it was decided that it was insignificant against the background current of 40 nA. We completed several tasks for the PARTICLE program over the course of our research. We tested 3 boxes of PMTs for gain and managed to redeem several PMTs that had been labeled bad. Paddles for the program were tested for light leaks using the picoammeter, and then fixed. James also designed and built 40 frames for the smaller scintillators. The previous mounts had been susceptible to problems because the PMT wasn’t supported or protected. This often caused the PMT to become dislodged or broken away from the optical epoxy that secured it. The new design protects and supports the PMT’s weight while still allowing for stable stacking of PMTs, which is required for many particle experiments. In order to try to get an approximation for appropriate voltages for the PMTs on the panels, we took background readings from both a PARTICLE paddle and the panel on a digital oscilloscope and analyzed the respective pulses. The amount of charge of each pulse was determined by integrating over the pulse width, and the peak voltage was read from a spreadsheet. The DAQ board is sensitive to peak voltage, but our source tests measured charge per unit time. The ratio of charge/peak voltage for the large panel to the small paddle should reflect the ratio of (Cs-137 source) panel to paddle current. (Q/V) panel = I panel (Q/V) paddle I paddle Consequently, PMT voltages are adjusted so that the current in the panel is proportional to the paddle by an amount derived from the pulse ratios. Using reading lamps to isolate a light leak A PMT mount with padding. Bolts driven through the boards on the right and a slot in the PVC allowed it to slide. The top was also hinged to allow easier access. Light leak testing performed on Quarknet panels by Paul Sedita. Wooden frame for Quarknet panel and PMT. Graph comparing net light current and light current/dark current ratio to the average of all of the Thorn tubes. Tubes were selected for their high net light current and similarity to another tube. Early frame before Joyce hanger installation Frame with board in place. The PMT mounts haven’t been attached yet in this photo. This diagram shows the dip in sensitivity in the middle of the panel, as well as the asymetry of the PMTs when both are run at the same voltage. The Daq: the piece of hardware used to detect hits from the panels. This table of efficiency data shows that the total lost hits (Channel count) is relatively low, but the PMTs are not very symmetrical in their hit count. Ideally Channel – and Channel 1 2 – 4 should be as close as possible while still maintaining a high efficiency. After a small voltage adjustment, the PMTs are almost perfectly symmetric in their count rates, and the efficiency isn’t largely impacted. The operating voltages chosen are higlighted in yellow. This map of efficiencies shows that there is approximately a 4% drop in efficiency in the middle of the board, however it always stays in a very acceptable range. We received four 10 ft by 2.5 ft scintillating panels from the Fermilab NuTev experiment. We removed the coverings off one of the panels that already had a huge rip in it to examine the construction. In order to perform coincidence experiments we selected two panels to eventually be mounted on top of each other and built wooden frames for them. After selecting matching PMTs and mounting them we tested for light leaks and fixed any problems we found. We then launched extensive tests to try to get symmetry between the slightly different tubes and optimize the efficiency. Working around the serial port bottleneck was a major focus to allow us to detect at the high speeds these panels allow. On the side several students working on PARTICLE program tasks. These included building custom frames and testing their PMTs with our setup and methods. The digital oscilloscope was triggered on the small paddles. The area under each curve (charge) should be proportional to the current output. The final adjustments to PMT voltage were made based on efficiency of muon count rates. Two particle paddles were aligned above and below the center of the panel, and paddle coincidence data was collected for 10 minutes in channels 1 & 2 of the Daq board. Concurrently muon counts from each panel PMT were registered in channels 3 & 4. When only channels 1 and 2 detected a hit, the muon was completely missed by the large panel. When 1, 2 and 3 fired (or 1, 2, and 4), one PMT detected a hit while the other did not register an event. Panel 2 has over 95% efficiency even at the center of the detector (the weakest detection area), and over the course of several trials excellent symmetry between the two PMTs was obtained by raising or lowering the voltage. For final panel operation, we made a junction box that sums the two inputs from the PMT’s. The passive signal addition splits the total signal in half. We therefore lowered our DAQ board threshold from 30 mV to 15 mV. An efficiency map of each panel was charted, showing that muons striking any part of the panel have ~ 95% likelihood of being registered in the summed signal by the DAQ board.

We received four 10 ft by 2.5 ft scintillating panels from the Fermilab NuTev experiment. We removed the coverings off one of the panels that already had a huge rip in it to examine the construction. In order to perform coincidence experiments we selected two panels to eventually be mounted on top of each other and built wooden frames for them. After selecting matching PMTs and mounting them we tested for light leaks and fixed any problems we found. We then launched extensive tests to try to get symmetry between the slightly different tubes and optimize the efficiency. Working around the serial port bottleneck was a major focus to allow us to detect at the high speeds these panels allow. On the side several students working on PARTICLE program tasks. These included building custom frames and testing their PMTs with our setup and methods.

One of our first tasks was to design permanent frames for the large scintillators. A ladder-like construct was chosen to be a light and strong way to proptect and support the 200 pound panels. 16 ft. boards were notched with a router for the crossbeams to fit, and Joist hangers were used for extra support. The crossbeams themselves were notched to provide a snug cradle for the metal frame of the plastic scintillators. These crossbeams prevented sagging in the middle of the panel and lay under complementary supports in the metal frame. The wooden frame provides excellent support without adding significant weight. The panel frames have thick side boards for support and to enable sturdy stacking for coincidence testing.

The experimental setup consisted of a diffuse light source (green LED embedded in an acrylic block with a small window to let out light) and a PMT placed in a darkbox. Using a picoammeter, output current from the PMTs was measured as a function of voltage. A gain curve was subsequently plotted for a range of 1.0 kV to 1.8 kV. Other components of the experiment included a pulse generator to regulate the 200 hertz LED flashes (a constant output from this LED would be enough light to burn out the PMTs), and an oscilloscope to view the output voltage pulses from the PMTs and the pulse width of the LED. The gain curves resulted in the choice of the Hamamatsu brand PMTs for use in the large scintillators due to their superior sensitivity and low dark current compared to the Thorn and PARTICLE PMTs we had available to test.

When designing the frame for the scintillator panels it was crucial to include sturdy support for the fragile PMTs on each end. Otherwise the PMTs are prone to being knocked off or damaged by someone walking by or sheer carelessness. PVC piping lined with foam padding was used to cradle the PMTs. The cradle was secured to the inside and bottom of the panel frame; thus providing ample support and protection. A sliding mechanism was also implemented to allow access to the PMT/panel connection without complete removal of the PMTs. Two different methods were used to attach the PMTs to the wave-shifting bar. The first consisted of a set of milled aluminum attachments designed for use with the Hamamatsu PMTs and these panels. A silicone cookie was placed between the PMT and the panel to provide mechanical protection and to minimize an air gap. For the second panel a foam shroud to hold an acrylic cookie was made and the PMT was attached using optical grease and electrical tape.

To test for light leaks the picoammeter was connected to the ExcelLinx program, which automatically records data to a spreadsheet. We did runs averaged over 500 readings and calculated the standard error for each. The first test for each panel was a series of lights on/lights off tests to see if there was any significant difference in current. One of the panels showed a noticeable change in current with the lights on. We proceeded to use reading lamps to illuminate the top, then the bottom of the board, using a picoammeter to try to detect where the leak was located. We also used a black cloth to selectively shroud sections of the panel. The leak was found near a PMT on panel 6 (which was subsequently fixed). The other panel showed a 2 nA drop in current with the lights off. The leak couldn’t be isolated and it was decided that it was insignificant enough to ignore.

We completed several tasks for the PARTICLE program over the course of our research. We tested 3 boxes of PMTs for gain and managed to redeem several PMTs that had been labeled bad. Paddles for the program were tested for light leaks using the picoammeter, and then fixed. James also designed and built 40 frames for the smaller scintillators. The previous mounts had been susceptible to problems because the PMT wasn’t supported or protected. This often caused the PMT to become dislodged or broken away from the optical epoxy that secured it. The new design protects and supports the PMT’s weight while still allowing for stable stacking of PMTs, which is required for many particle experiments.

In an effort to create the most efficient and symmetric detection with the panels we tested each panel with a series of Cs-137 gamma source runs. The source was placed over grid locations on the panel and the summed net current of both PMTs was averaged over 100 samples and recorded with ExcelLinx. Because individual PMTs proved to have slightly different gain, we altered the voltages to get better symmetry. We also mapped individual PMT currents across the whole panel and determined that muon hits further than the middle of the board were not very likely to be detected by the opposite PMT.

In order to try to get an approximation for appropriate voltages for the PMTs on the panels, we took background readings from both a PARTICLE paddle and the panel on a digital oscilloscope and analyzed the respective pulses. The amount of charge of each pulse was determined by integrating over the pulse width, and the peak voltage was read from a spreadsheet. The ratio of charge/peak voltage for the large panel to the small paddle should reflect the ratio of (Cs-137 source) panel to paddle current. (Q/V) panel = I panel (Q/V) paddle I paddle Consequently, PMT voltages are adjusted so that the current in the panel is proportional to the paddle by an amount derived from the pulse ratios.

In an effort to create the most efficient and symmetric detection with the panels we tested each panel with a series of Cs-137 gamma source runs. The source was placed over grid locations on the panel and the summed net current of both PMTs was averaged over 100 samples and recorded with ExcelLinx. Because individual PMTs proved to have slightly different gain, we altered the voltages to get better symmetry. We also mapped individual PMT currents across the whole panel and determined that muon hits further than the middle of the board were not very likely to be detected by the opposite PMT. For final panel operation, we had a junction box made that sums the two inputs from the PMT’s. To compensate for loss of signal voltage we halved the threshold of the Daq board to 15 mV. An efficiency map of each panel was charted, showing that muons striking any part of the panel have ~ 95% likelihood of being registered in either PMT.

The serial connection between the DAQ and the computer was originally baud. The DAQ sends a 73 byte * 8 bit signal, which means at 100% efficiency the maximum speed of detection is about 32 hertz. By viewing the onboard hex counter the panel achieves about 260Hz, but only 30Hz was seen on the computer. The speed was increased to baud and the data format was compressed to 12 bytes. Currently, there are still concerns that data loss is occurring and work is being done to correct it.